Centrifugal Investigation of Excavation Adjacent to Existing Composite Foundation

This paper discusses an experimental investigation, by centrifuge tests, of excavation behavior adjacent to existing composite foundations, with the aim to understand excavation-induced lateral earth pressures and deformation mechanisms and so assist the design of preliminary retaining structures for excavation. In particular, the behavior of excavated composite foundations was investigated based on centrifuge model tests. Experimental studies concentrated on excavation-induced lateral earth pressures, bending moments of retaining structures, lateral deformation, and ground settlement. This further led to a detailed investigation of the resulting deformation mechanism of excavated composite foundations and its influence on the safety of overlying structures and the economic design of side retaining structures. Moreover, the effects of different surcharge load amplitudes (i.e.,representing overlying buildings of different heights) on the behavior of excavated composite foundations were analyzed through parametric experimental studies. Based on the experimental results, the following conclusions can be drawn: (1)excavation-induced earth pressures in the composite foundation are smaller than the Rankine active earth pressures in the depth range of the excavation, indicating that the Rankine method for predicting active earth pressure is conservative for the excavation problems in a composite foundation; (2)the excavation-induced bending moment is observed to peak at approximately 3m below the corresponding excavation bottom; (3)the relation between excavation-induced settlement and distance from the excavation can be assumed to be exponential; (4)greater surface load induces larger lateral earth pressure amplitudes and bending moments on the retaining pile raft, whereas the position of the maximum bending moment is consistent regardless of the load amplitude.